Porous building materials produced from illite-containing lime-free and lime-rich clays with organic and inorganic additives were studied. The frost resistance, thermal conductivity, pore size distribution and pore structure were determined. The Maage index of frost resistance was calculated. Factory-fired and laboratory-fired samples were prepared. Bricks from lime-free clays were fired at 980-1000 C, while those from lime-rich clays were fired at 1000-1020 C. The pores in the ceramic bodies are formed in two ways: between the layers of the clay minerals; and in the texture of the body between the phases newly formed by decomposition of carbonates. Due to their high density and a pore size of about 1 micron, bricks prepared from lime-free clay have high thermal conductivity and frost resistance, while those prepared from lime-rich clay have low values. Fine additive (wood dust) considerably lowers the frost resistance. The lowest conductivity and highest frost resistance were achieved using a combined additive (2-5% sawdust; 8.5-12% chamotte; and 5% limestone powder). 13 refs.
Primary author(s): Svinka R; Svinka V; Cimmers A; Moertel H; Certoks S
Riga,Technical University; Erlangen-Nurnberg,University